1. Field of the Invention
The present invention is directed to a magnetic resonance tomography apparatus and magnetic resonance method for operating the device.
2. Description of the Prior Art
Magnetic resonance transmission methods and tomography apparatuses are known wherein a pulse generator drives a high-frequency modulator with a pulse with a generator amplitude and a generator phase, the high-frequency modulator actuates a high-frequency power amplifier, the high-frequency power amplifier emits an analog output signal with an actual amplitude and an actual phase to a magnetic resonance transmission antenna, a scanning signal that corresponds to the output signal is supplied to a pulse controller, which compares the actual amplitude with a set amplitude and the actual phase with a set phase and which determines correction values for the generator amplitude and the generator phase and supplies these to the pulse generator for emitting a further pulse, and wherein, between pulses, a magnetic resonance reception antenna supplies an analog magnetic resonance reception signal of an object to a magnetic resonance reception receiver, which emits a digital intermediate signal as an output.
Such known magnetic resonance transmission methods and magnetic resonance transmission arrangements that correspond therewith are used to generate exactly reproducible output signals for a longer period of time.
In the known methods and apparatuses, the output signal is acquired and is supplied to an analog regulator circuit. The regulator circuit has to be designed with high precision, temperature-stable and therefore expensive components.
An object of the present invention is to provide a magnetic resonance transmission method and a magnetic resonance transmission arrangement which are operable without high precision components.
This object is achieved in a magnetic resonance transmission method in An accordance with the invention wherein a fraction of the output signal is supplied to the aforementioned magnetic resonance receiver during the pulses and the thus-obtained intermediate signal which is emitted is supplied to the pulse controller as a scanning signal, and wherein the pulse controller digitally processes the intermediate signal.
This object is achieved in a magnetic resonance transmission arrangement in accordance with the invention wherein the decoupling element is also connected to the magnetic resonance receiver, and the magnetic resonance receiver is connected to the pulse controller, and the pulse controller is fashioned as a software controller.
Due to the usage of the magnetic resonance receiver that is present anyway, a dedicated component is not required for the processing or preparation of the fraction of the output signal. Moreover, a regulator that does not require high precision components and that exhibits a hitherto unachieved flexibility results from the digital regulation, which preferably ensues in a microprocessor.
For example, the pulse can be one of a number of pulse types, with a type-specific set amplitude, a type-specific set phase and type-specific correction values being stored for each pulse type. The type-specific set amplitude and the type-specific set phase and, if necessary the type-specific correction values as well, are consulted for determining the correction values.
Corresponding herewith, the magnetic resonance transmission arrangement has a pulse type identifier and a memory for storing and retrieving type-specific set amplitudes, type-specific set phases and type-specific correction values.
It is also possible for the determination of the correction values to ensue only when a correction request is allocated to the pulse.
The set amplitude and the set phase are preferably determined by generating a preset number of pulses, determining the actual amplitude and the actual phase for each of these pulses forming average values before the amplitude regulation and phase regulation are performed.